async_xor: convert to dmaengine_unmap_data
async_xor: convert to dmaengine_unmap_data

Use the generic unmap object to unmap dma buffers.

Later we can push this unmap object up to the raid layer and get rid of
the 'scribble' parameter.

Cc: Vinod Koul <5cf69c63beb17bf38d63aa0e923ee8256af0e205@intel.com>
Cc: Tomasz Figa <c4885e520559c7b5b4fe1e9e188b924d2debd35e@samsung.com>
Cc: Dave Jiang <7a72b0ecdf501e4593e842e1a61bf3d5b53699e6@intel.com>
Reported-by: Bartlomiej Zolnierkiewicz <24970bf3d8506c473367e9292a8e5eb43a40bda0@samsung.com>
[bzolnier: minor cleanups]
Signed-off-by: Bartlomiej Zolnierkiewicz <24970bf3d8506c473367e9292a8e5eb43a40bda0@samsung.com>
Signed-off-by: Kyungmin Park <504c23c4986a3760712724894be3105092c27331@samsung.com>
Signed-off-by: Dan Williams <24ee2bf0bd8ac766c348bf1f0639943bac1535c6@intel.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs